Why, for saturated steam, as the pressure increases and the temperature rises, does the enthalpy value decrease?
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After saturated steam reaches a certain temperature and pressure, when the pressure and temperature are increased, why does the higher the pressure and temperature, the lower the enthalpy value?
It would be best to provide the source so that we can see the original text and facilitate discussion.
No way – the enthalpy of saturated steam increases as pressure rises, while the heat of vaporization decreases as pressure increases.
The higher the saturated vapor pressure, the smaller the difference between vapor and liquid. Once the critical pressure and temperature are reached, the vapor cannot be converted into a liquid, and vapor and liquid become one. Therefore, for heat exchange, the lower the pressure of the saturated steam, the higher the efficiency.
I checked the appendix to the principles of chemical engineering – indeed, for steam at pressures above 3 MPa, the enthalpy of the steam decreases as the pressure increases: lol